Mechanical activation of cement with addition of fly ash

Abstract

Influence of mechanical activation on quality of cement with addition of fly ash was investigated. The experiments of mechanical activation were performed in laboratorial vibro mill with rings. The effects of mechanical activation were determined by the comparative analyses of the starting cement and the same cement treated mechanically for 3, 10 and 30 min. The analyses included determination of the specific surface area, X-ray diffractometric analysis (XRD), differential-thermal analysis (DTA) and thermogravimetric analysis (TGA). During the 30-min comminution period, the specific surface area was increasing, while the microstructural changes of portland cement with fly ash addition (20% wt.) were intensified. DT and TG analyses show that endothermic and exothermic reactions proceed at the lower temperatures, which is an indication of increased reactivity of mechanically activated sample. Physico-mechanical properties significantly improved after only 3 min activation. After the 3-min activation, i.e., the seven-day solidification, the increase in the compression strength is very well-expressed. However, even after the 28-day solidification, the compression strength of mechanically activated sample was 58% higher, in comparison with inactivated sample of the same composition. Also, after the 28-day solidification, the compression strength of portland cement with addition of fly ash, mechanically activated for 3 min, was approximately the same to the compression strength of portland cement without additives.